A write-once optical disk known under the acronym CD-R is broadly used in computer technology and is nowadays implemented in most of the current PCs and notebooks. However, data amounts to be stored are increasing continuously, resulting in the demand for higher storage capacity. Rewritable DVD's (DVD-RAM, DVD-RW, DVD+RW) are on the market, having a storage capacity of 4.7 GB. Furthermore, a next generation of large capacity optical discs called “Blu-ray Disc” has recently been announced, enabling the recording, rewriting and play back of up to 27 GB of data. This allows e.g. archiving computer data with high capacity or recording of two hours high-definition television video.
Defects occurring during the writing process have to be addressed in order to avoid re-writing the whole data, resulting in the case of write-once media in the use of a further disk. This is especially important for realtime recording of audio-visual (AV) data streams on write-once media or rewritable media and realtime playback of such recorded streams, since defects would result in very annoying interrupts of the picture or audio signal.